1. Field of the Invention
The present invention relates to a pedal support structure for a vehicle, and particularly to a pedal support structure for supporting a brake or clutch pedal.
2. Discussion of the Related Art
A brake pedal for a vehicle is provided in front of a seat for a driver in a passenger compartment. The brake pedal has a pedal pad and a pedal lever, and is actuated by a driver. The pedal pad is used as a step-on (treadle) surface which the driver stamps. The pedal lever extends approximately in a vertical direction and has the pedal pad at a bottom end thereof. A top end of the pedal lever is supported on a pedal bracket so as to pivot thereon and the pedal bracket is fixed to a toe board. The toe board is a partition interposed between an engine compartment and the passenger compartment. In front of the toe board, i.e., on an engine compartment side with respect to the toe board, a master cylinder is provided for amplifying the stepping force by the driver. The master cylinder and the pedal lever is linked with each other via a pushrod.
There is such a possibility that the brake pedal with the above-mentioned structure is moved rearward, that is, in a direction toward a passenger when an external force, larger than a predetermined force is applied to the vehicle from the front. In this case, the external force pushes a power unit rearward, and the power unit pushes the master cylinder and the toe board toward the passenger compartment. Finally, the brake pedal supported by the pedal bracket is pushed rearward. In that event, there is such a possibility that a large load is applied to a foot placed on the pedal pad.
As a countermeasure to eliminate such possibility, several kinds of pedal support structures are proposed. One of the pedal support structures is, as shown in FIG. 8, contains a master cylinder 111 located in front of the toe board 101, namely on the side of the engine compartment. The master cylinder 111 and a front end of the pedal bracket 112 are connected to the toe board 101. On the other hand, a rear end 113 of the pedal bracket 112 is connected to a bulkhead 102 which horizontally extends on an upper end of the toe board 101 by fixing means 114. The fixing means 114 connects the pedal bracket 112 with the bulkhead 102 so as to make the pedal bracket 112 detachable from the bulkhead 102 when the pedal bracket 112 rearwardly moves with respect to the bulkhead 102.
FIG. 9 is a cross section of FIG. 8 which is cut along a line 9-9 of FIG. 8. As shown in the figure, the fixing member 114 contains a circular bolt hole 116 perforated in the bulkhead 102, and a bolt hole 117 having a portion 117a with a small diameter connected with a portion with a large diameter 117b. The portion 117b with a large diameter is provided in front of the portion 117a with respect to the lengthwise direction of the vehicle. The portion 117a with a small diameter is made so as that a shaft part of a bolt 115 can be inserted with remaining a small space between the portion 117a and a shaft part of the bolt 115. On the other hand, the portion 117b with a large diameter is prepared so as that a bolt head can pass through. The bolt 115 is inserted into the portion 117a with a small diameter as a part of the bolt hole 117 in the pedal bracket and the bolt hole 116 in the bulkhead 102. Then, the bolt 115 is screwed into a welded nut 118, and hence the pedal bracket 112 and the bulkhead contact and are connected to each other as shown in FIG. 8. The clamping force of the bolt 115 is set so as to keep the bracket 112 slidable with respect to the bulkhead 102 in a rear direction when a load in a rearward direction is applied to the pedal bracket 112 in the case of a collision.
As shown in FIG. 8, a downwardly inclined surface 103 is formed on the bulkhead 102. The inclined surface 103 is placed so as to face the rear end 113 of the pedal bracket 112, and rearwardly inclines toward a rear part of the vehicle. An upper end of a brake pedal 120 is supported by the pedal bracket so as to pivot thereon. The pedal 120 pivots in a lengthwise direction of the vehicle. Moreover, a pushrod 123 rearwardly extends from the master cylinder, and is linked to an intermediate part of the brake pedal 120. This structure is described, for instance, in Japanese Kokai Publication 10 (1998)-310036.
When a vehicle with the above-mentioned structure collides, the master cylinder 111 moves rearwardly with the deformation of the toe board 101. The pedal bracket 112 fixed to the toe board 101 rearwardly moves with respect to the bulkhead 102. By the rearward movement of the pedal bracket 112, the bolt 115 moves from the portion 117a with a small diameter to a portion 117b with a large diameter. The bolt 115 passes through the portion 117b with a large diameter. Accordingly, the connection between the pedal bracket 112 and the bulkhead 102 is released, and finally the pedal bracket 112 falls down by being disconnected from the bulkhead 102.
The pedal bracket 112 disconnected from the bulkhead 102 further moves rearwardly. Then, the rear end 113 of the pedal bracket 112 contacts the inclined surface 103, and the rear end 113 are downwardly pressed by the guidance of the inclined surface 103. As a result, the brake pedal 120 supported by the pedal bracket 112 pivots so as to forwardly move a pedal pad 102 provided at the bottom of the brake pedal 120. In this way, the master cylinder 111 and the pedal bracket 112 can rearwardly move by a frontal collision, the forward pivotal movement of the bottom of the brake pedal 120 helps to cancel (offset) the rearward movement of the master cylinder 111 and the pedal bracket 112. Therefore, the above-mentioned structure can decrease a load which could be applied to a foot or a leg of a passenger placed on the pedal pad 121 of the brake pedal 120 in the case of collision.
In the brake pedal support structure described in Japanese Kokai Publication 10 (1998)-310036, it is possible to prevent the brake pedal 120 supported on the pedal bracket 112 from moving toward a passenger compartment.
On an actual collision, however, the pedal bracket 112 detached from the bulkhead 102 may complicatedly move until the bracket 112 reaches the inclined surface 103. When the bulkhead 102 deforms, the inclined surface 103 could be deformed. Thus, the pedal bracket 112 detached from the deformed bulkhead 102 can behave in a complicated manner. Therefore, it is extremely difficult to assume (estimate) the behavior of the pedal bracket 112 and the pedal 120 supported by the pedal bracket 112. Hence, it is difficult to perform tuning of the support structure under estimating possible movement of relevant members, and there is such a possibility that safety for a passenger is not sufficiently attained.
On the other hand, when the pedal bracket 112 with a brake pedal or other member fitted thereto is mounted to a vehicle, an accurate positioning of members have to be carried out. Namely, it is necessary that the portion 117a with a small diameter formed in the bulkhead 102 have to be accurately positioned with respect to the bolt hole 116 in the pedal bracket 112. The bulkhead 102 and the pedal bracket 112 have to be connected by a bolt 115 after the positioning with high accuracy. When the accurate assembly cannot be obtained, the detaching behavior of the pedal bracket 112 from the bulkhead 102 becomes unstable. Based on the unstable detachment, the pedal bracket 112 also behaves in an unstable manner and it is possible that a desired effect cannot be obtained by the unstable behavior.
Since the pedal bracket 112 has to be mounted on a vehicle within a limited space in a passenger compartment of a vehicle, the mounting accuracy cannot always be attained. If the pedal bracket 112 is not accurately mounted, it is possible that the reliability on safety is decreased.